The invention relates to a multipart rim having an interior part of the rim or wheel spider for mounting at an axle, as well as having annular exterior parts that are located radially on the outside of the rim at both the inner and outer sides of the interior part of the rim or wheel spider to form a tire bed.
The use of multipart tire rims are commercially known. Multipart construction offers the advantage that different interior parts of the rim or wheel spiders may be combined with different exterior parts of the rim in order to develop or adapt the tire rim to different vehicles and different tire sizes or widths. These multipart tire rims can be sold as kits with various sized external parts.
Since the unsprung masses of vehicles, particularly high-speed vehicles, should be as low as possible, and since tire rims constitute a considerable part of the unsprung vehicle masses, it is basically desirable for the weight of the tire rims to be as low as possible. In this connection, multipart rims made of a light metal on the basis of aluminum and/or magnesium are known. However, even a further weight reduction is desirable. This goal cannot be achieved by means of conventional light metals.
Metallurgists know that components capable of withstanding extreme stress can be manufactured from titanium with an extremely low weight, as shown by the example of rotors for turbines of airplanes. Even though titanium alloys exist from which deformable sheets can be Produced by pressing and drawing, the processing of titanium materials is extremely costly, particularly when workpieces are to be produced that have complicated shapes. Thus, although it is basically possible to manufacture rims from titanium, it has not been possible to do so economically.
It is therefore an object of this invention to provide an economically produceable rim that distinguishes itself with respect to known, commercially available lightweight construction rims by a clear reduction in weight accompanied by the ability to withstand high stress.
This objective is achieved by the fact that the interior part of the rim or wheel spider consists of titanium (or a similar highly stressable lightweight material), and the exterior parts of the rim that are connected or can be connected with the interior part of the rim or wheel spider, consist of light metal using aluminum, magnesium and/or plastic.
The invention relies on the general idea of manufacturing only the interior part of the rim or wheel spider, that is particularly important with respect to the stability of the rim, of titanium or a lightweight material of the highest stability that may be hard to process, while the exterior parts of the rim consist of a material that is easier to handle, even when the shape thereof is complicated.
In the case of this construction, the interior part of the rim or wheel spider, that is dimensioned essentially only according to aspects of strength and stability, may be developed to be approximately disk-shaped, or as a part with relatively flat convexities, or of an uncomplicated shape which can be produced from titanium sheet metal at still limited cost, for example, by a deformation in the superplastic condition.
In order to provide the rim with a particularly attractive design, the outside of the interior part of the rim or the wheel spider which faces away from the axle, may completely, or only in a central area, be covered by a cover that preferably consists of the same material as the exterior parts of the rim that form the tire bed. Use of such a material allows for a construction or arrangement that gives the impression this exterior facing material also has a load carrying function, or is in a load carrying connection with the exterior parts of the rim. However, as this material actually has no load carrying function, the cover may have an extremely light weight.
This aesthetic construction allows the interior part of the rim or wheel spider that consists of titanium or the like to be constructed exclusively according to technical load and strength aspects, while at the same time, the visual appearance of the rim can be changed slightly by the changing of the cover.
A particularly high stiffness, with a narrow wall thickness and a correspondingly low weight, can be achieved by means of the fact that the interior part of the rim or wheel spider has a central area that serves for fastening the rim onto a wheel hub or a flange at the hub and that, with respect to the exterior area, is arranged to be axially offset, for example, recessed, in top view of the front side of the rim.
According to one embodiment of the invention, the central area of the rim that is used for the fastening of the wheel at the axle is essentially plane or flat, while radially outside of the central area of the rim, the rim configuration preferably continues as a conical zone that, toward the outside, is followed by a torus.
The torus itself may then continue toward the outside as a preferably approximately planar ring or flat annular zone which, in turn, at the outer circumference of the interior part of the rim or wheel spider, may be bent in the direction of the front side of the rim, particularly to its interior side.
In addition, in the transition area between the torus and the annular zone that connects it toward the outside, openings may be arranged, the edges of which, at least at the areas extending approximately in a radial direction of the rim, are bent out or arched out toward one side of the rim, particularly toward the side of the torus.
As a result of the above-described shape of the interior part of the rim or wheel spider, a high so-called buckling strength is achieved with a narrow wall thickness of the interior part of the rim or wheel spider, which leads to a high ability to withstand stress.
The indicated shaping of the rim is possible by deforming titanium sheets in the superplastic condition, i.e., when the sheet is heated to about 1,000.degree. C. Thus, conventional processes that are known for the working of sheet metal may be used. The titanium sheet metal must only undergo a corresponding additional heating for the deformation
In order to achieve a connection of the interior part of the rim or wheel spider with the exterior parts of the rim forming the tire bed, where the interior part is as highly stressable as possible, it may be advantageous to provide the radially exterior part of the rim that is arranged on one front side of the radially interior part of the rim or wheel spider with a front web area that fits onto an outer edge of the interior part of the rim or wheel spider
In addition, this exterior part of the rim which carries the tire and/or the exterior part of the rim that carries the tire and is arranged on the other front side of the interior part of the rim or wheel spider may both be provided with an axial annular web portion which rest firmly without play on the outer circumferential edge of the interior part of the rim or wheel spider, for example, on an outer circumferential surface of its bent outer edge.
With this construction, connecting devices, such as screws, that are used for the holding of the exterior wheel carrying parts of the rim to the interior part of the rim or wheel spider are not stressed in a radial direction, i.e., in the direction of particularly high stress to the rim during the driving operation.
Advantageously, suitable components of conventional multipart rims are used as much as possible for the tire bed of the rim according to the invention. This applies particularly to the front parts of the rim that carry the tire and which form the front edges of the tire bed. However, conventional front parts of the rim cannot simply be mounted at an interior part of the rim or wheel spider that consists of titanium because, as a result of the narrow material thickness of the titanium part in comparison to the conventional interior parts of the rim or wheel spiders made of steel, aluminum, or magnesium, a tire bed would be obtained that is too narrow. Therefore the mounting of the front parts of the rim that carry the tire and that form the front edges of the tire bed may take place by means of a ring-disk. This ring-disk has a first axial ring web at its outer circumference, located on the side of the interior part or the rim or wheel spider which extends over the outer edge of the interior part of the rim or wheel spider without or practically without any radial play. This ring-disk also can be provided with a second axial ring web with portions at its inner circumference, facing away from the interior part of the rim or wheel spider that reaches under an interior edge of a ring flange of the respective front part of the rim that holds the tire without or practically without any radial play
If ring-disks are arranged on both sides of the interior part of the rim or wheel spider, the first ring webs that face one another at the exterior of the interior part of the rim or wheel spider may be additionally connected with one another in a form-locking way, by means of meshing projections and grooves or the like. These grooves and projections are located on the parts of the webs that face each other. One web can have only grooves with the other only projections, or each web can have both opposing grooves and projections. In each case, the projection on one web would face and mesh with a groove on the other web.
Also, the above-mentioned rings webs can be welded together while the ring-disks are prestressed with respect to one another so that the ring-disks, after the welding-together, rest on the front sides of the interior part of the rim or wheel spider made of titanium or the like with a corresponding tension.
In a way that is known per se, the front parts of the rim may be secured axially by means of studs or the like that are arranged in an annular shape and penetrate the ring flanges of the front parts of the rim, the ring-disks, and the radially exterior area of the interior part or the wheel spider.
These and other objects, features, and advantages of the present invention will become more apparent from the following description when taken in connection with the accompanying drawing which show, for the purposes of illustration only, plural embodiments in accordance with the present invention, and wherein: